Introduction

The Principles of GIScience (GISCI 242) paper I took in Semester 1 2022 taught and assessed my network analysis skills. The assignment focused on the catchment area of the Mt Eden train station in Auckland. Walking, cycling, and transit connectivity were the perspectives to examine to gain insight on the accessibility of the train station via public transport. I used ArcGIS Pro to carry out the network analysis and produce maps for which I received an A+ grade.

Walkability

# reading and resizing image
knitr::include_graphics("lab4_map1_pedrestrian.png")

Map 1 displays the catchment area of people within a reasonable walking distance of the Mt Eden Train Station (METS). According to Burke and Brown (2007), the distance people are willing to walk to a train station (to the 85th percentile) is 1.57km. The METS sits between the Kingsland and Grafton train stations, so if pedestrians are based closer to to these than the METS they will use them instead which poses a multi-facility service area problem.

Using the network analysis tool, the Mt Eden, Grafton, and Kingsland train stations were selected as facilities. The output created standard precision split polygons with impedance set to length and a 1570 meter cut off. The METS polygon was exported to a new layer and intersected with the mesh blocks layer to find out the serviced population.

0.86% of the 2013 Auckland population was potentially within walking distance of the METS. This was concluded after turning the mesh blocks into centroids using the feature to point tool to exclude mesh blocks that only fractionally intersected with the walking catchment.

Bus Transit Connectivity

# reading and resizing image
knitr::include_graphics("lab4_map2_bus.png")

Map 2 shows the catchment area of people served by bus stops that service the METS. Using the select by location tool, two bus stops within 100m of the METS were identified: 8502 and 8503. Using AT live departures, 25B, 25L, 27H, 27T, and 27W were identified as the routes that would facilitate transport to the METS. These routes were exported to a new layer using the select by attribute tool. In total, 210 bus stops were found along these routes by creating a dissolved 10 meter buffer around them and then using the intersect tool to identify the bus stops within the buffer.

To determine the walking distance catchment of these bus stops, a service area was created. Using the bus stops as facilities, impedance set to length with the cut-off being 400 meters - the median distance people are willing to walk to bus stops. The output was a dissolved standard precision polygon, exported to a new layer.

Finally, the bus catchment was reduced by removing the walking catchment (displayed in map 1) using the erase tool. Based on the assumption that people would rather walk to the METS in that area. The areas north of the walking catchment were also removed using the explode tool as a commuter would not travel away from the CBD to get back to the CBD.

3.76% of the 2013 Auckland population was potentially served by bus to commute to the METS. This percentage was calculated using centroid containment.

Cyclability

# reading and resizing image
knitr::include_graphics("lab4_map2_bike.png")

Map 3 displays the reasonable catchment area of people within a 15-minute bike ride of the METS. The service area was analyzed using the Kingsland, Grafton, and Mt Eden train stations as facilities. The cut-off was set at 3000 (as 15 minutes by bike equates to 3 km, assuming cycle speed is 12 km/hr). The output was split standard precision polygons to exclude the population closer to the Kingsland and Grafton train stations. The western part of the catchment that stretched along the expressway and the part north of the expressway were also excluded because commuters cannot cycle along the expressway. If they were located north of the express way, it was assumed they would not cross the express way and go straight to the CBD instead. This reasonable catchment potentially services 1.54% of the 2013 Auckland population.

Suspending the reasonable criterion of excluding the northern and western catchment areas, the cycle catchment potentially services 2.1% of the 2013 Auckland population. This percentage was calculated using centroid containment.

Conclusion

The METS potentially served 4.78% of Auckland’s population in 2013 by walking, bussing, and cycling. This percentage was calculated by merging the catchments from maps 1, 2, and 3 that were produced with the ‘reasonable’ criterion and intersected with centroid contaminants. Centroids give a more conservative estimate than using the mesh blocks that are only within the total catchment by a fraction.

This HTML file was created using R Markdown in RStudio.

@import url('https://fonts.googleapis.com/css2?family=Nanum+Gothic&family=Ultra&display=swap');

h1 {font-family: 'Ultra', serif;
    background-color: #ffffff;
    text-align: center;
    color: #030059;}
        
h2 {font-family: 'Ultra', serif;
        background-color: #ffffff;
        text-align: center;
        color: #278036;}
        
body {font-family: 'Nanum Gothic', sans-serif;
      background-color: #ffffff;
      padding: 10px;
      color: #193416;}